Over 1000 exoplanets have been discovered, but not a single moon as been uncovered, until now. (Photo: Shutterstock)

Despite the fact that astronomers have identified over 1000 possible planetary systems, the discovery of the first exomoon - a natural satellite that orbits a planet outside of our Solar System — has remained elusive, up until now. However, scientists recently uncovered what could be the best exomoon candidate yet: first moon which could be 1,800 light years away.

Like Us on Facebook

The possible discovery comes from a group of scientists studying microlensing, led by David Bennett, an astrophysicist at the University of Notre Dame in Indiana. The possible discovery was reported in a paper posted on the arXiv preprint server1 on December 13th of this year.

Two years ago on a June night, a telescope in New Zealand captured a quick flash of a brightening star in the constellation Sagittarius. This rare phenomenon known as microlensing occurs when a celestial body comes directly between earth and a distant star resulting in the magnification of the light of the faraway star.

Bennet's team detected an initial event where a distant star's light was amplified to almost 70 times its normal brightness, followed an hour later by smaller increase in brightness. This led the astronomers to believe that a larger object, followed by a small one, passed in front of the star. It was not clear, however, whether the two objects are for sure a planet and its moon - it could also have been a small star and an orbiting planet. The observation unfortunately cannot be repeated, so a 100 percent degree of certainty can never be achieved.

One thing that is certain is that these two objects are moving through space unhinged to any solar system — an observation that is interesting in its own right.

Either way, the observation raises questions about how an exoplanet and its exomoon getting that way. There could be billions of rogue planets unbound to any star wandering the cosmos, according to at least one other microlensing study, says Nature magazine. They were possibly unhinged out of their stellar systems and lost any accompanying moons through violent gravitational interactions.

"An apparently free-floating planet with a half Earth-mass moon would be a new class of system that was not previously known to exist," write Bennett and his team. "Such a new discovery would require strong evidence, so our favored model for this event is that it is a low-mass star or brown dwarf orbited by a planet of about Neptune's mass." Although the event happened two full years ago, Bennett and his team have kept quiet on the subject, preferring to wait until their findings are published in a peer-reviewed journal.

Of course, the reason exomoons are so intriguing is that scientists speculate that some of these moons may be large and hospitable enough to host extra-terrestrial life. There is no data yet to show whether this particular discovery could indicate any sort of alien life.